1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, the present invention is best suited when applied to a semiconductor device using a resin insulating film such as polyimide, BCB, or the like.
2. Description of the Related Art
Conventionally, a resin insulating film such as polyimide, BCB, or the like is generally used as a front face protective film for a chip mounted by mold etc.
An example of a chip using an insulating film such as polyimide, BCB, or the like as a front face protective film is shown in FIG. 8A to FIG. 8E. FIG. 8A and FIG. 8B are plane views showing a front face of the chip. FIG. 8C is a sectional view taken along the Vxe2x80x94V line in FIG. 8B. FIG. 8D is a sectional view taken along the VIxe2x80x94VI line in FIG. 8B. FIG. 8E is a bottom view showing a reverse face of the chip.
On an operating layer of a semiconductor substrate 101, a source electrode, a gate electrode and a drain electrode are formed in a shape of teeth of a comb. A source pad 102, a gate pad 103 and a drain pad 104 are respectively led out from the respective electrodes on the front face of the semiconductor substrate 101.
The upper side of the operating layer of the semiconductor is covered with a surface protective insulating film 105 such as polyimide etc. A view in FIG. 8A shows a specification in which only the upper side of the operating layer is covered with the surface protective insulating film 105. A view in FIG. 8B shows a specification in which all the regions except the respective pad areas 102 to 104 are covered with the surface protective insulating film 105. Thus, exposure of the electrodes and the semiconductor area on the front face of the chip is reduced so as to take a structure aiming for improvement of reliability.
Generally on the chip as structured above, the source pad 102 is connected to a pad 102A on the reverse face of the chip through a via hole 102B, and the pad 102A on the reverse face is mounted as ground of the source.
As described above, an insulating film such as polyimide, BCB, or the like is often used as a front face protective film of a conventional chip. However, a device using polyimide or BCB cannot be utilized for application which requires a high reliability. For example, polyimide has a high water absorbing property and would be saturated with absorbed water in the long term. Then, the water would be soaked out up to fingers such as the gate, the source, and the like to induce corrosion, ion migration, and so on. Therefore, there could be a risk of causing a device trouble. On the other hand, BCB is said to have an extremely small water absorbing property. However, interface between metal and BCB, and BCB itself would be permeated with water. Therefore, there could be a risk of causing the aforementioned trouble.
Due to the above-described problems related to moisture resistance, a highly airtight hermetic seal package is used for a device which requires higher reliability. However, a hermetic seal package is extremely expensive and in some cases it costs several times as much as a chip. Therefore, it will be a big barrier when trying to reduce costs of the product.
The present invention is made in view of the aforementioned problems. Therefore, it is an object of the invention to obtain a highly reliable semiconductor device having a significantly improved moisture resistance while using an insulating film such as polyimide, BCB, or the like.
The present invention is made in view of the aforementioned problems. Here, metal is focused on because it is easily available, is easily subjected to microfabrication, is a general material used in semiconductor manufacturing, and has a high moisture resistance. Therefore, metal is used to cover all of an upper surface and side surfaces of polyimide, BCB, or the like which is applied as an insulating film above the front face of the semiconductor substrate. That is, in the semiconductor device according to the invention, the front face of a semiconductor chip is covered protectively with the insulating film as well as the whole surfaces of the aforementioned insulating film is covered with a metal protective film having moisture resistance.
A problem when covering the insulating film with metal is that metal is conductive. It is needless to say that the chip cannot work when formed by a usual electrode forming method because all exposed electrodes and pads etc. will be short-circuit. Consequently, in this invention a structure is adopted so that all the necessary electrodes are led out from the front face to the reverse face. In other words, the semiconductor device according to this invention includes a plurality of electrodes connected to an active region on the front face of the semiconductor chip, a resin insulating film provided on the aforementioned active region, a metal protective film covering all of the upper surface and the side surfaces of the aforementioned resin insulating film, and one or a plurality of electrical connecting portions of the reverse face provided at the reverse side of the aforementioned semiconductor chip, leading out at least one electric potential of the aforementioned plurality of electrodes to the reverse face.
Additionally, a manufacturing method of a semiconductor device according to this invention includes a step of forming a plurality of electrodes on a front face of a semiconductor chip, a step of covering the front face of the aforementioned semiconductor chip with a resin insulating film, a step of covering all of the upper surface and the side surfaces of the aforementioned resin insulating film with a metal protective film, and a step of providing an electrical connecting portion of at least any of the aforementioned plurality of electrodes at the reverse face of the aforementioned semiconductor chip.